The overall objective of this proposed investigation is to continue to identify and define the role of cell surface antigens expressed by murine nervous tissue. Certain cell surface components associated with lymphoid tissue have been postulated to be involved in cell-cell recognition and interaction phenomena. A key example is the Thy-1 differentiation alloantigen which has been purified, physiochemically characterized and shown localized at the synapse. The initial phase of this investigation will entail attempts to further define the cellular and subcellular distrbution of Thy-1 in mouse brain cerebellum at varying ages utilizing immunocytochemical labelling techniques. In particular, attempts will be made to demonstrate relationships between the expression of Thy-1 with certain functional characteristics such as neurotransmitter content. This background of information will serve to allow selection from the broad array of synaptic membrane components those molecules which are expressed exclusively on functionally distinct subsets of synaptosomes, on cells in discreet anatomical regions within the brain and at precise developmental stages. This phase of the investigation will require partial or complete characterization of synaptic membrane components and the generation of heterologous antiserum as well as monoclonal antibody. The latter reagents will be utilized to correlate the expressin of antigens so defined with developmental and functional events. Lastly, an embryonic mouse brain aggregate culture system will be adapted in an effort to describe the functional role for each cell surface component identified by resorting to quantitative assessment of specific perturbations of synaptogenesis via electron microscopic examination. This project should further expand knowledge with regard to the structural-functional relationships of synaptic cell surface antigens which dictate the events involved in the establishment and/or maintenance of the synapse.